The present invention relates to oxocarbon-, pseudooxocarbon- and radialene compounds as well as to their use as organic doping agent for doping an organic semiconductive matrix material for changing its electrical properties, as blocker material as well as charge injection layer and as electrode material. The invention also relates to organic semiconductive materials as well as to electronic components in which the oxocarbon-, pseudooxocarbon- and radialene compounds are used.
In the present application alicyclics in which all ring atoms are sp2-hybridized and to the extent possible carry exocyclic C—C double bonds are designated as radialenes, see also H. Hopf and G. Maas, Angew. Chem. (1992), 8, 955. Oxocarbon- and pseudooxocarbon compounds are sufficiently known as non-benzoid aromatics, see, e.g., G. Seitz, Nachr. Chem. Tech. Lab. 28 (1980), pages 804-807. The first oxocarbon compound, potassium croconate, was produced by L. Gmelin in 1825 from potash and coal. Those compounds, in which at least one oxygen atom is replaced by another heteroatom, are designated as pseudooxocarbons, as is readily known to an expert in the art.
It has been known for several years that organic semiconductors can be heavily influenced regarding their electrical conductivity by doping. Such organic semiconductive matrix materials can be built up either from compounds with good electron donor properties or from compounds with good electron acceptor properties. Strong electron acceptors such as tetracyanoquinonedimethane (TCNQ) or 2,3,5,6-tetrafluoro-tetracyano-1,4-benzoquinonedimethane (F4TCNQ) have become known for the doping of electron donor materials (HT), M. Pfeiffer, A. Beyer, T. Fritz, K. Leo, Appl. Phys. Lett., 73 (22), 3202-3204 (1998). and J. Blochwitz, M. Pfeiffer, T. Fritz, K. Leo, Appl. Phys. Lett., 73 (6), 729-731 (1998). They generate so-called holes by electron transfer processes in electron donor-like base materials (hole transport materials) by the number and mobility of which holes the conductivity of the base material is more or less significantly changed. For example, N,N′-perarylated benzidines TPD or N,N′,N″-perarylated starburst compounds such as the substance TDATA, or, however, also certain metal phthalocyanines, such as in particular zinc phthalocyanine ZnPc are known as matrix material with hole transport properties.
However, the previously described compounds have disadvantages for a technical use in the production of doped semiconductive organic layers or of corresponding electronic components with such doped layers since the manufacturing processes in large-scale production plants or those on a technical scale can not always be sufficiently precise, which results in high control- and regulating expense within the processes for achieving a desired product quality or in undesired tolerances of the products. Furthermore, there are disadvantages in the use of previously known organic donors with regard to electronic components such as light-emitting diodes (OLEDs), field effect transistors (FET) or solar cells themselves since the cited production difficulties in the handling of the doping agents can lead to undesired irregularities in the electronic components or in undesired ageing effects of the electronic components. However, it should be considered at the same time that the doping agents to be used have extremely high electron affinities (reduction potentials) and other properties suitable for the application case since, e.g., the doping agents also co-determine the conductivity or other electrical properties of the organic semiconductive layer under given conditions. The energetic positions of the HOMO of the matrix material and of the LUMO of the doping agent are decisive for the doping effect.
The present invention has the task of overcoming the disadvantages of the state of the art, in particular to make new organic mesomeric compounds available that can be used in particular as doping agent for the doping of organic semiconductors, that can furthermore be more readily handled in the production process and that result in electronic components whose organic semiconductive materials can be reproducibly manufactured
This task is solved, at least in part, by the following organic mesomeric compound and/or the use of the organic mesomeric compound as organic doping agent for the doping of an organic semiconductive matrix material, as blocker layer, as charge injection layer or as organic semiconductor itself, characterized in that the mesomeric compound is an oxocarbon-, pseudooxocarbon- or radialene compound with the following formula:
in which n=1-4; each X1, X2, X3, X4, and X5 is independently selected from the group consisting of C(CN)2, (CF3)C(CN), (NO2)C(CN), C(halogen)2, C(CF3)2, NCN, O, S, NR1,
in which Y═CN, NO2, COR1 or is perhalogenated alkyl; aryl or Ar is a substituted or unsubstituted, aromatic hydrocarbon or biaryl, optionally polycyclic; hetaryl is a substituted or unsubstituted aromatic heterocyclic compound or biheteroaryl, preferably electron-poor, optionally polynuclear or partially or completely hydrogenated or fluorinated; and R1-R8 are independently selected from hydrogen, halogen, CN, NO2, COR1, alkyl, alkoxy, aryl and heteroaryl. In one embodiment, Y is perfluoroalkyl, including, for example, CF3. In another embodiment, aryl or Ar is partially or completely hydrogenated, or partially or completely fluorinated. In a further embodiment, hetaryl is selected from pyridyl, pyrimidyl, triazine, or oxadizole. In a still further embodiment, R1-R8 are independently selected from perhalogenated and/or partially halogenated alkyl groups, including, for example, perfluorinated alkyl groups.